Hatcher Pass

All the avalanches pictured below (except this first one)occurred in the afternoon on Friday, April 16th at approx. 1200′ on S and SE aspects. No other avalanches were observed or reported at mid or upper elevation this week.

Numerous wet loose avalanches were also observed on the S/SW aspect of Idaho Peak up to 3500′ on 4/16.

Road cut , AM 4/16

Road cut, PM 4/16 Wet loose triggers wet slab and takes out the metal fence panels.

4/16 Avalanche #1 near the Avalanche Gate at Gateway Natural Wet Loose triggered Wet-Slab that almost hits the road. 1200′ S/SE aspect .

4/16 Avalanche #2 near the Avalanche Gate at Gateway Natural Wet Loose triggered Wet-Slab that almost hits the road. 1200′ S/SE aspect

4/16 Avalanche #2 and #3 near the Avalanche Gate at Gateway Natural Wet Loose triggered Wet-Slab that almost hits the road. 1200′ S/SE aspect

Wet slabs will be a unlikely in the morning, RISING to CONSIDERABLE in the afternoon and likely to human trigger, on East, Southeast, South, and Southwest aspects, at LOW elevation, below 2500′,on slopes above 35º. Naturals will be unlikely in the morning and possible in the afternoon. It will also be possible for wet-loose avalanches to triggers wet-slab avalanches, as seen Friday at 1200′ on the road cut above the Raney homestead, and with 3 other additional wet-slabs at 1200′ near the avalanche gate at the entrance to Hatcher Pass.

Low elevation has reached a tipping point as a result of a sudden increase in temperatures this week. Snow surfaces are moist to wet on E to SW aspects below 2500′. Temperatures at 2700′ have hovered at or above freezing for 3 nights in a row. 3 nights above freezing is our general rule of thumb for predicting wet slabs combined with other factors.  We are not expecting it to freeze below 3000′ for the next several days.  Wet loose avalanches are predictable with time of day, but wet slabs are trickier to predict and follow long periods of above freezing temperatures and can be large in size.

Outlook: Temperatures are forecasted to rise throughout the weekend and into early next week. If it does NOT freeze for 3 nights in a row at 3000′ expect wet-slabs to be possible to likely at mid-elevation, or up to 3500′. We recommend using conservative decision making and widening your safety margin in and around southerly aspects this weekend.

Natural wet-loose that triggered a wet-slab at the road cut. 4/16 1200′ S/SE aspect. The debris took out the metal fencing.  This is an indicator of what to expect at mid elevation in the coming days to week with an increase in temperature.

Wet-slab avalanche near the avalanche gate, gateway to Hatcher Pass. This small path appears to have run 400 ft , making it close to the road. HPAC has never seen this path run this far before. 4/16 S/SE 1200′

Wet loose avalanches will be unlikely to human trigger in the morning, and likely to human trigger in the afternoon on E to S to SW aspects below 3500′, on steep slopes above 40º. Naturals will be possible in the afternoon. Significant warming this week has contributed to instability in the snowpack. Wet snow exists in the top 12″ of snow up to 2500′. Moist snow exists in the top 3-5″ from 2500′ to 3200′.  Temperatures will reach 45ºF over the next few days up to 4000′.

Wet-loose has the potential and likelihood of triggering a wet-slab, increasing the size and consequence of any avalanche. Wet loose are predictable and avoidable. Rollerballs are an indicator that it is time to move to a cooler aspect.

Natural Wet loose natural shown at approx. 1200′ on a S/SE aspect, likely occurred in the afternoon on 4/15. Numerous other wet-loose naturals were observed on the SW aspect of Idaho Peak on 4/16.

Persistent slabs, 1 to 3 feet deep will be possible to human trigger today at all elevations, on all aspects. Wherever the persistent slab did not fail during the Easter Avalanche Cycle will be suspect with increasing temperatures over the weekend. It will take more force to affect the buried facet/crust weak layer which in some locations is up to 5 feet deep, however it will be more likely in shallower locations on E,SE,S,SW,W aspects. Large cornice fall will also be capable of triggering a persistent slab avalanche.